In one embodiment, the present invention relates to catalysts which are useful in hydrogenation reactions and which comprise the oxides of copper and chromium, and at least one extrudable inorganic binder material.
Copper chromite catalysts have been used for many years to hydrogenate carbonyl compounds and functional side rings of aromatic compounds. For example, aldehydes can be hydrogenated to the corresponding alcohols, and fatty acids or methyl esters of fatty acids can be converted to saturated fatty alcohols.
Various types of catalysts and catalyst mixtures containing copper, chromium and alumina have been described in the literature. Generally, the copper and chromium are deposited on alumina supports. U.S. Pat. No. 2,741,618 describes a catalyst for use in the production of pyridine from pyrans comprising 93-99% activated alumina, 0.5-5% copper, 0.2-2.0% chromium and less than 0.1% of an alkali metal sulfate. U.S. Pat. No. 2,795,600 describes a chromium promoted copper and activated alumina catalyst containing less than 10% of calcium, barium, lithium or strontium. The catalyst is reported to be useful for the production of nitriles by the vapor phase reaction of primary alcohols and ammonia.
U.S. Pat. Nos. 3,781,406 and 3,883,445 describe an auto exhaust catalyst containing 2 to 15 parts by weight of copper, 0.1 to 10 parts by weight of chromium and 1 to 15 parts of a rare earth metal on 100 parts of alumina support. The alumina is a transition alumina, preferably gamma alumina and is in the form of an extrudate or the like.
U.S. Pat. No. 3,787,322 describes a catalyst for oxidation reactions at high temperatures which comprises a mixture of aluminum oxide of the gamma series with oxides of copper and chromium, the aluminum oxide being present in from about 20 to 45% of the total weight of aluminum oxide and the oxides of copper and chromium. The mole ratio of copper oxide to chromium oxide expressed as CuO.Cr.sub.2 O.sub.3 is from about 1.2:1 to 2.2:1. The catalyst may contain barium and may be prepared using a mineral acid such as nitric acid, or an organic carboxylic acid as an extrusion aid.
U.S. Pat. No. 3,855,388 describes a method of preparing an extruded copper chromite-alumina oxidation catalyst, and the catalyst is described as being useful for treating exhaust gases from internal combustion engines. Stearic acid is described as an extrusion aid, and acetic acid is described as a peptizing agent in Example 1.
U.S. Pat. No. 4,666,879 describes an extruded copper chromite-alumina hydrogenation catalyst which is prepared by blending copper chromite and an extrudable alumina typically having a pseudoboehmite or an alpha-hydroxy boehmite structure. The extruded and calcined catalyst is useful for the liquid and vapor phase hydrogenation and hydrogenolysis of various carbonyl compounds and the functional side groups of aromatic compounds. The extruded catalyst is characterized in this patent as having a surface area of between 20 and 225 square meters per gram and a packed apparent bulk density of between about 0.70 and about 1.20 g/cc. Small amounts of other materials may be included in the catalyst. For example, the catalyst can contain up to 10% by weight of a stabilizer selected from the group consisting of barium and manganese. Furthermore, small amounts of silica (for up to 15%) can be added to the catalyst along with the alumina, either to replace a portion of the alumina or as a supplement thereto.